Multimedia communication sessions such as voice and video calls over Internet Protocol (IP) may use defined signalling protocols such as the Session Initiation Protocol (SIP). Such a protocol can be used to create, modify, and terminate two-party (i.e. unicast) or multi-party (i.e. multicast) sessions comprising one or more media streams. Other example uses of protocols such as SIP include, without limitation, video conferencing, streaming multimedia distribution, instant messaging, presence information, file transfer, and online gaming.
Traditional SIP-based solutions such as those implementing voice over IP (VoIP), are either server based, thus using a registrar to identify the users of the system and their states, and a proxy to connect users together; or peer-to-peer (P2P), wherein the central servers are removed and the individual nodes form a mesh network in which any node can be reached from any other node, usually within six hops.